DNA, RNA contaminants
Contaminants

[2012 Sept] Fragments of Foreign DNA and Other Substances From Vaccines Found in Disabled and Dying Children by Christina England

[2012 Sept] Unveiling the Culprit Is Foreign DNA Contamination the Autistic Villain behind Biologic Vaccine Injuries? By Leslie Carol Botha

Genetically engineered vaccines 'Inherently unpredictable and possibly dangerous'

There is the problem of DNA & RNA contamination of vaccines